In NGN (Next Generation Network), the difficulty in ensuring quality of service (QoS) of a service is increased because the bearer network adopts packet technology, especially IP (Internet Protocol) technology.
In order to ensure the QoS of a service, the concept of resource and admission control and its corresponding function entity are incorporated into NGN. Resource and admission control is located between a service control layer and access/bearer layer for shielding specific access/hearer layer technology and topology information from entering the service control layer, and implementing that resource and admission control related functional entities receive service related QoS request from the service control layer, combine it with admission control policy, topology information of the network and so on, and convert the service QoS information into IP QoS information which is transmitted to related access/bearer layer node and service gateway node, then these nodes achieve corresponding QoS control according to the received information and their own functions.
ITU-T (ITU-Telecommunication Standardization Sector) and ETSI (European Telecommunication Standards Institute) are two organizations that are dedicated to setting NGN technology standards, and regarding resource and admission control, they put forward RACF (Resource and Admission Control Function) and RACS (Resource and Admission Control Subsystem) respectively.
Although scopes of the drafts of the resource and admission control systems of the two organizations are different and definitions on some specific function entities are not exactly same, their frames are similar and compatible.
In the draft regarding RACF, the ITU-T provides a functional frame of RACF as shown in FIG. 1.
FIG. 1 includes the following function entities: SCF (Service Control Function), PD-FE (Policy Decision Function Entity), TRC-FE (Transport Resource Control Function Entity), PE-FE (Policy Execute Function Entity), TRE-FE (Transport Resource Execute Function Entity), NACF (Network Attachment Control Function), CPE (Customer Premises Equipment) and so on.
SCF is used for controlling negotiation on a service layer and initiating a resource request to RACF according to QoS negotiated in the service session.
PD-FE is used for making a preliminary QoS resource decision based on session information of media stream and transport resource subscription information (referred to as subscription information in short) of the user obtained from NACF, then interacting with TRC-FE to confirm whether there is enough QoS resources, making a final decision, and handing the decision down to PE-FE for execution.
TRC-FE is mainly responsible for resource control, monitoring the resources in the network and collecting related information, making a response according to the specific resource status when PD-FE requests resources.
PE-FE is mainly responsible for performing policy control under the direction of PD-FE, such as door control, bandwidth, traffic classification and label, traffic shaping, Layer 2 and Layer 3 QoS mapping, collecting and reporting information about resource use, and so on.
TRE-FE performs Layer 2 policy execution under the directions of TRC-FE.
In a draft of ETSI TISPAN (Telecommunication and Internet converged Services and Protocols for Advanced Networking) regarding RACS, a functional frame of RACS is provided as shown in FIG. 2.
FIG. 2 includes the following function entities: AF (Application Function), SPDF (Service-based Policy Decision Function), x-RACF (generic Resource and Admission Control Function), NASS (Network Attachment Subsystem), BGF (Border Gateway Function), RCEF (Resource Control Enforcement Function), L2TF (Layer 2 Termination Function) and so on.
AF is a service control function for controlling negotiation on a service level and initiating a resource request to RACF according to QoS negotiated in the service session.
SPDF selects a local policy according to the request from the AF, and maps the request to an IP QoS parameter, which is then transmitted to A-RACF and BGF for applying for corresponding resources.
x-RACF is divided into C-RACF (Core-Resource and Admission Control Function) and A-RACF (Access-Resource and Admission Control Function).
A-RACF receives a request from SPDF, and then implements admission control based on the stored policy by accepting or refusing the request for transmitting resources. A-RACF can obtain network attachment information and QoS subscription information of the user (referred to as subscription information in short) from NASS through e4 reference point, thus determining available network resources according to network position information (e.g., the address of the physical node accessing the user terminal), meanwhile referring to the subscription information of the user when processing the resource distribution request.
BGF is located between an access network and a core network for implementing core border gateway function; it can also be used as a gateway between two core networks. BGF implements functions such as NAT, gate control, QoS label, bandwidth restriction, use measurement, resource synchronization and so on under the control of SPDF.
RCEF implements functions including gate control, QoS label and bandwidth restriction by Layer 2/Layer 3 (L2/L3) media steam policy defined by an accessed operator transmitted via Re reference point.
L2FT is a function entity terminating Layer 2 connection in the access network. RCEF and L2TF are two different logical function entities that can be usually implemented in one physical equipment.
In a NGN system, the current process of QoS negotiation of the session service is as follows: firstly, QoS negotiation of a service is performed on a service control layer, and then SCF/AF initiates a resource request to RACF/RACS according to the negotiated QoS of the service, RACF/RACS makes an admission decision according to the subscription information of the user and the current status of available resources; if it can be admitted, then the policy is handed down to the policy execute entity in the transmission layer; if the total of the requested resources and the resources that have been used by the user exceeds the resources subscribed by the user, or the requested resources exceed the currently allocatable resources, then the resource request of SCF/AF will be refused.
FIG. 3 is an illustration for the flow in which a resource request of a service is refused in the prior art, and it specifically comprises the following steps of:
301: CPE/UE initiating a service request to SCF/AF, the request containing expected QoS information;
The above QoS information comprises: upstream bandwidth, downstream bandwidth, priority and so on.
302: if the QoS of the service request can be accepted by the service layer, SCF/AF initiating a resource request to RACF/RACS according to QoS requested by the user;
303: if RACF/RACS does not have subscription information of the user, RACF/RACS interacting with NACF/NASS to obtain subscription information of the user;
304: RACF/RACS making an admission decision in response to the request according to the subscription information and the current status of available resources; if the total of the requested bandwidth and the bandwidth which has been used by the user exceeds the resources subscribed by the user, or the requested bandwidth exceeds the currently distributable bandwidth in the equipment on the transmission layer, then the resource request will be refused;
305: RACF/RACS transmitting a resource request refusing message to SCF/AF to refuse the resource request;
306: SCF/AF transmitting a service request refusing message to CPE/UE to refuse the service request; and
307: initiating service session negotiation again between CPE/UE and SCF/AF if necessary.
It can be seen from above that since the current RACF/RACS only returns a related error code when there are not enough resources to inform SCF/AF of the reasons for refusing a resource request, SCF/AF can only blindly negotiate with the user again, making resource requests repeatedly, or speculatively reduces requirement on resources to apply for less resources because the specific status of resources has been shielded by RACF/RACS although it knows that the resource request is refused due to lack of resources.
Using a method repeatedly making resource requests, the application cannot succeed until other applications release resources; using a method of speculatively reducing requirement on resources, it is impossible to know to what extent the requirement has to be reduced in order to successfully applying for resources, since no basis can be used as a reference, therefore efforts may be made for many times in order to successfully applying for resources, which is much less efficient.